Novel rinsing agents

ABSTRACT

A PROCESS FOR MECHANICAL DISHWASHING IN WHICH THE CLEAR RINSING CYCLE EMPLOYS A WATER-SOLUBLE STARCH DEGRADATION PRODUCT AND/OR SUGAR TO OBTAIN SPOT-FREE DISHES AND NOVEL RINSING SOLUTIONS.

United States Patent Oflice Int. Cl. Clld US. Cl. 252-89 Claims ABSTRACTOF THE DISCLOSURE A process for mechanical dishwashing in which theclear rinsing cycle employs a water-soluble starch degradation productand/ or sugar to obtain spot-free dishes and novel rinsing solutions.

PRIOR ART Known dishwashing methods with dishwashing machines have shownthat it is most advantageous to use two cleaning agents, one in thecleaning process for thorough removal of food particles from the chinapieces and a clear rinsing agent during the final rinse to obtainlustrous and dry dishes. Clear rinse agents have been used for a longtime and by their surface active agents, the surface tension of thewater is reduced in the final rinse which effects a film-like drainageof the water from the dishes. The said water film shall be drained offas long as possible without interruption. Any slight remaining traces ofwater are rapidly evaporated by the heat retained by the china from thewash step or by subsequent heating, or by ventilating, etc. The cleaneddishes then can be removed from the dishwasher in a dry and shinycondition. However, the known neutral clear rinse agents containing asurface-active agent are not able to safely prevent calcareous depositsand the development of stains with water having a high degree ofhardness. Moreover, heavy foam formation may occur and interfere withthe washing step.

To avoid these disadvantages, attempts have been made to acidify theclear rinse agents with inorganic acids such as phosphoric acid ororganic acids such as lactic acid, tartaric acid or citric acid. Theseacid additives prevent an accumulation of calcium deposits from hardWater and give spot-free dishes and satisfactory clear-dry effects.However, the use of these acidified clear rinsing agents has thedisadvantageous effect on the stability of porcelain glazes and glassdecor. Although the acid agents alone do not cause any noticeableeffect, considerable corrosion phenomena may occur when they are used incombination with alkaline cleaning agents. This is caused by thealternate alkaline and acid treatment of the decoration whereby thealkaline agent might extract silicate ions therefrom While the acidclear rinse agent might leach metallic oxides from the glaze.

OBJECTS OF THE INVENTION It is an object of the invention to provide anovel process for machine washing of dishes without spotting.

It is another object of the invention to provide a dishwashing processwhich will avoid calcium deposits without adversely affecting dishes.

These and other objects and advantages of the invention will becomeobvious from the following detailed description.

THE INVENTION The novel dishwashing process of the invention for machinewashing of dishes comprises first washing dishes with an alkalinewashing agent and then rinsing the washed dishes with an aqueous rinsesolution containing about 0.1 to 2.0 gm. per liter of at least oneneutral rinse Patented July 13, 1971 agent selected from the groupconsisting of water-soluble starch degradation products and sugars. Thesaid process unexpectedly gives an outstanding luster to the dishes andavoids calcareous deposits, corrosion phenomena and foam formation.Moreover, the rinse agents have the advantage of being physiologicallyacceptable.

Examples of suitable rinse agents are sugars such as glucose, lactose,particularly cane sugar and beet sugar and starch degradation productsby action of enzymes or acids on starch, soluble dextrins, etc. The saidsugars or degradation products may be in refined form or in crude formsuch as baking syrup or molasses.

In dish washing cycles in which a drying step follows the rinse step, acompletely satisfactory clear-dry effect is obtained by the sole use ofsugars or starch degradation products in the rinsing step. Fordishwashing cycles with no final drying step, it is preferred to add anon-ionic or anionic surface active agent to the rinse agent.

Examples of suitable additives to the rinse agent are non-ionic, lowfoaming surface active agents such as (A) adducts of ethylene oxide withfatty alcohols of 8 to 22 carbon atoms or alkyl phenols having 2 to 16alkyl carbon atoms; (B) adducts of ethylene oxide with polypropyleneoxide having a molecular weight of 500 to 2000; (C) adducts of propyleneoxide to adducts of group (A) and (D) sugar esters of fatty acids of 8to 20 carbon atoms.

The novel rinse agent concentrates of the invention are comprised of anaqueous solution of 20 to 50% by weight of at least one agent selectedfrom the group consisting of sugars and water-soluble starch degradationproducts and 0 to 20% of a water-soluble organic solvent. The use of theorganic solvent improves solubility of the concentrates. Examples ofsuitable water-soluble organic solvents are lower alkanols such asethanol, propanol, isopropanol, etc. The concentrates can optionallycontain 1 to 20% by weight of a non-ionic or anionic surface activeagent. The concentrated rinsing agent may be added by manual measurementor preferably by an automatic dosing device.

In the following examples there are described several preferredembodiments to illustrate the invention. However, it should beunderstood that the invention is not intended to be limited to thespecific embodiments.

EXAMPLE I Normally soiled dishes were cleaned in a commercialdishwashing machine having a drying cycle with an aqueous alkalinecleaning solution heated to 55 to 70 C. and containing 1.4 gm./l. ofsodium tripolyphosphate, 0.56 gm./l. of sodium metasilicate and 0.04gm./l. of potassium dichloroisocyanurate and rinsed with clear water at60 to 70 C. and containing 0.12 gm./l. of an admixture of saccharose andmolasses. The rinse water had been softened to a hardness of 1 bypassing it through a cation exchanger and the dry residue amounted to0.56 gm./l. The said washing cycle gave a satisfactory clear-dry effect.

EXAMPLE II The process of Example I was repeated with the exception thatthe clear rinse water contained 0.1 gm./l. of molasses and 0.01 gm./l.of a mixture of an adduct of 20 moles of ethylene oxide with one mole ofnonylphenol and an adduct of first 9 moles of ethylene oxide and then 10moles of propylene oxide with one mole of nonyl phenol. This clearrinsing composition proved satisfactory in the commercial dishwashingdevice of Example I and in dishwashers without a drying cycle.

EXAMPLE III Dishes were washed in a three-cycle dishwashing machineusing in the first cycle an aqueous alkaline cleaning solution at 55 to70 C. and containing 2.1 gm./l. of

3 sodium tripolyphosphate, 0.84 gm./l. of sodium metasilicate and 0.66gm./l. of potassium dichloroisocyanurate, clear rinse water having ahardness of 16 in the second cycle and in the third cycle clear aqueoussolution at 60- 70 C. and containing 0.18 gm./l. of an admixture ofsaccharose and molasses. After 150 cycles of washing, nocalcium-containing deposits were observed on the dishes or in themachine and the clear-dry effect was perfect and there were no adverseeffects on the porcelain overglaze decorations.

EXAMPLE 1V Using the procedure of Example 111, dishes were washed whichused in the clear rinsing cycle a solution containing 0.15 gm./liter ofmolasses and 0.5 gm./liter of adduct of by weight of ethylene oxide withpolypropylene glycol and having a molecular weight of 1750. Even after150 cycles of washing, a perfect clear-dry effect was obtained with nodeposits on the rinsed dishes or in the dishwasher and without anycorrosion phenomena.

EXAMPLE V Water having a 16 German hardness originally and which hadbeen hardened to a 30 German hardness by the addition of calciumchloride was used in the following rinse test in which the necessaryamount of rinse water used in common household diswashers was taken fromthis source. The dishes were washed with an alkaline cleaning solutioncontaining 3.5 gm. per liter of sodium tripolyphosphate, 1.4 gm. perliter of sodium metasilicate and 0.1 gm. per liter of potassiumdichloroisocyanurate. The clear rinsing solution contained 0.27 gm. perliter of an admixture of saccharose and molasses to obtain a cleardryeffect. After 150 cycles of washing, there were no calcareous depositsor corrosion signs on the dishes or the dishwasher.

EXAMPLE VI The process of Example V was repeated except that the clearrinse solution contained 0.31 gm. per liter of molasses and 0.08 gm. perliter of an equal mixture of the adduct of 20 moles of ethylene oxidewith 1 mole of nonylphenol and the adduct of 5 moles of ethylene oxidewith 1 mole of nonylphenol and the adduct of 5 moles of ethylene oxideand 13 moles of propylene oxide with 1 mole of coconut oil alcoholshaving 12 to 18 carbon atoms. An excellent clear-dry effect withoutcalcareous deposits on dishes and the dishwasher and without any crazingof the porcelain overglaze decorations was noted after 150 cycles ofwashing.

Various modifications of the compositions and method of the inventionmay be made without departing from the spirit or scope thereof and it isto be understood that the invention is to be limited only as defined inthe appended claims.

I claim:

1. A process for machine washing of dishes comprising first washingdishes with an alkaline washing agent and then rinsing the washed disheswith an aqueous rinse solution consisting essentially of 0.1 to 2.0 gm.per liter of neutral sugar rinse agents.

2. The process of claim 1 wherein the rinse agent is selected from thegroup consisting of cane sugar, beet sugar and dextrin.

3. The process of claim 1 wherein the neutral rinse agent also contains1 to 20% by weight of a low foaming nonionic surface active agent.

4. The process of claim 3 wherein the surface active agent is a sugarester of a fatty acid of 8 to 20 carbon atoms.

5. The process of claim 3 wherein the surface active agent is a loweralkylcne oxide adduct of at least one member of the group consisting ofethylene oxide and propylene oxide.

6. The process of claim 1 wherein the neutral rinse agent is an aqueousconcentrate containing 20 to by weight of the rinse agent.

7. A rinse agent concentrate for machine washing of dishes consistingessentially of an aqueous solution of 20 to 50% by weight of neutralsugar rinse agents.

8. The concentrate of claim 7 containing 1 to 20% by weight of annonionic surface active agent.

9. The concentrate of claim 7 containing up to 20% of a lower alkanol.

10. The concentrate of claim 7 wherein the agent is selected from thegroup consisting of beet sugar, cane sugar and dextrin.

References Cited UNITED STATES PATENTS 3,062,878 11/ 1962 Karabinos etel. 252-89 3,074,927 1/1963 Saltman et al. 25289 3,082,172 3/1963 Templeet al. 25289 3,481,881 12/1969 Wedell 252-89 FOREIGN PATENTS 211,6463/1966 Australia 252-89 OTHER REFERENCES Mehltretter et al. I:Sequestration of Sugar Acids, Incl. & Eng. Chem., December 1953, pp.2782-2784.

Mehltretter et al. II: New Low Cost Sequestrants, Soap & Chem Spec.,August 1969, pp. 49, 50 and 106.

LEON D. ROSDOL, Primary Examiner W. E. SCHULZ, Assistant Examiner U.S.Cl. X.R. 1342: 252--

